正向构造对层间氧化带砂岩型铀矿成矿和定位的控制

The controlling role of positive structures over the metallogenesis and emplacement of inter layer oxidation sandstone type uranium deposits

正向构造指的是与铀矿带或铀矿床产出位置相关的背斜、隆起、上升断块等矿床地质构造。伊犁盆地南缘、吐哈盆地西南缘、酒东盆地东北缘等砂岩型铀矿成矿带的产出特征表明,层间氧化带砂岩型铀矿床、矿段和矿点总是选择性地就位于正向构造之中。其原因在于层间氧化带砂岩型铀矿的成矿机理所决定。即正向构造抬升了容矿层位,使其出露或接近地表,容易接受补给区含氧含铀水的渗入,造成主砂岩层的层间氧化,铀在主砂岩层中迁移,并在氧化还原界面还原成矿。因此,正向构造对氧化带砂岩型铀矿成矿和定位的作用应引起足够重视,它可以作为产铀盆地砂岩型铀矿带成矿远景区段识别和预测的一项重要判据。

The positive structures in this paper mean the geological structures related to the occurrence of U-metallogenic zones or U-deposit such as anticlines,uplifts and uplifted fault-blocks.Occurrence features of interlayer oxidation sandstone type deposit at the southern margin of Yili basin and southwestern margin of Turpan-Hami basin,the northeastern margin of Jiudong basin illustrate that the sandstone-hosted uranium deposits,the U-mineralized sections and the uranium occurrences are always selectively emplaced on/in positive structures.The reasons for this lie in the formation mechanism of sandstone-hosted U-deposits.The positive structures raised the elevation of ore-hosting sandstone horizon and make it close to ground surface or exposed at the ground surface,which result in the infiltration of uranium and oxygen bearing groundwater from recharge area into host sandstone horizon,and the interlayer oxidation of host sandstone,as well as the dissolution and the migration of uranium in host sandstone,and the reduction mineralization at the oxidation-reduction interface.Sufficient attention should be paid to the controlling role of positive structures over the metallogenesis and emplacement of sandstone-hosted uranium deposits.They could act as an important criterion for recognizing and prognosticating potential uranium mineralized areas in uranium metallogenic zones or uranium-productive sedimentary basins.